Topic: 1972 cb500 petcock and fuel lines

[yogi]

HI all,

I was draining my fuel tank and noticed that gas was only coming out of one fuel line. If I covered that line gas would start coming out of the other line but stop on the first. Is this normal, or is something wrong?

[yogi]

Here is an answer to my own question (maybe?). I attached some clear fuel filters and noticed that once the bike was running gas, seemed to flow through both lines. I'm guessing that when the hoses are not attached, as gas flows out one line then air goes in the other, but when the lines are attached, the air comes through the gas cap and gas can flow out both tubes. Am I right (and this would be normal)?

[Deltarider]

 Inline fuel filters are known to cause problems on a CB500. They can do this intermittently which makes it even harder to diagnose. Don't ask me how I know. When the petcock filter is still there and in good order, there's NO need for any inline filter whatsoever. These 'extra' filters often hinder a constant flow and btw so do fuel lines that are not standard and as a result can kink. With the appropiate length and diameter of the fuel lines (for your model that's: 18 and 30 cm resp., ⌀ 5,5 mm), it is practically impossible to route them wrongly > guaranteed no kinking. This may not be an answer to your question but I have given' up reflecting on alternatives. Stay standard and you'll be fine, is all I can advise you..

[goldarrow]

One line feed left two carbs, the other line feed right two carbs, once bowls on one side filled up, the other side started to flow and fill up the bowls.  Perfectly normal. 

[dave500]

like delta ive never liked extra filters I think they aint needed and are an extra cause of leaks,if the stock one is in good shape they work fine,the bowl has a tiny well in the bottom to collect debris,i managed to find a tiny circular magnet that dropped straight into it to hopefully collect ferrous crap from the odd times I stop at remote crappy looking filling stations,i check the bowl once a year and its always clean.

[strynboen]

yes delta and dave hit it.
.only vaccum can make those problems..so thek the filler cap breate hole too...a small vaccum in the fuel tank..can do strange Things to the fuel flow